Breaking the Rules: Dynamic Navigation in Modularized Apps

Properly handled navigation is critical for modularized apps, which often implement navigation logic at runtime. This presents certain challenges when working with the Navigation Components library:
* How do we determine NavDestinations that are in other libraries, without access to their NavGraphs?
* How do we change the way backstack fragments behave based on past NavDestinations?
* How do we safely maintain state for each Fragment in the backstack?

And not least - how can we solve all of these issues when working with Compose?

Add in multiple modules and multiple libraries, and writing clean navigation logic can get really messy. I’ve dealt with all of these complexities when working on heavily modularized applications. I’ll walk the audience through the lessons I learned, and how to push the Navigation library capabilities to the fullest extent.

Transcript

1. breaking the rules: dynamic navigation in modularized apps sumayyah ahmed
2. about me Github: https://github.com/sumayyah LinkedIn: https://www.linkedin.com/in/sumayyah-ahmed
3. Everything is modularized Everything is scoped encapsulated reusable what could be better?
4. how do we navigate?
5. A B
6. A B
7. A B
8. A B A B
9. nav components introduced scoping
10. Activity NavHostFragment NavController Nav Graph XML: All the destinations in the flow Handles communication between view layer and nav logic
11. Activity NavHostFragment NavController Nav Graph Handles communication between view layer and nav logic Compose version 1 - interoperable Composable Composable Fragment Composable Composable Fragment
12. Composable NavHost Nav Graph Handles communication between view layer and nav logic Compose version 2 - 100% Compose Activity Composable Composable Composable NavHostController
13. A B
14. Module A Module B Module C
15. Module A Module B Module C NavGraph Activity NavGraph Activity NavGraph Activity NavGraph Activity
16. Module A Module B Module C NavGraph Activity NavGraph Activity NavGraph Activity NavGraph Activity ?
17. default: maintain encapsulation
18. NavGraph NavGraph Module A Module B Activity A Activity B
19. by default, navigation is static
20. what if you have unknowns at runtime? what if navigation is custom to a particular user type? A->B->C is different from D->E->C?
21. navigation can be dynamic
22. now let’s start breaking the rules
23. Graph A Fragment A Fragment B Fragment C Fragment A Activity A Graph 1 Activity B Graph 2 Fragment A Fragment B Fragment C Fragment A
24. Graph A Fragment A Fragment B Fragment C Fragment A Activity A Graph 1 Activity B Graph 2 Fragment A Fragment B Fragment C Fragment A deep links
25. Destination Graph 25
26. Destination Graph 26 Source
27. Destination Graph 27 Source Graph
28. Destination Graph 28 Source Graph
29. Destination Graph 29 Source Graph Source Code
30. Case 1: Interoperable Compose Activity NavHostFragment NavController Nav Graph Composable Composable Fragment Composable Composable Fragment
31. Deep linking remains the same! Case 1: Interoperable Compose
32. Destination Graph 32 Source Graph Source Code
33. Case 2: 100% Compose Composable NavHost NavHostController Nav Graph Activity Composable Composable Composable
38. Destination Graph 38
39. Destination Graph 39 Source Graph
40. Destination Graph 40 Source Graph Source Code
41. Destination Graph 41 Source Graph Source Code
42. how does the navigation work?
43. inflation time!
44. NavController SparseArray<NavDestination> NavGraph::class.java NavDestination NavDestination NavDestination mNavGraph BackStack via Activity reference Fragment 1 NavGraph Fragment 2
45. Navigator<T> NavDestination T::class.java Deep Links Actions Declared in code Created by NavComponents Actions Navigator<T>
46. Navigator<T> NavDestination T::class.java Deep Links Actions Declared in code Created by NavComponents Actions Navigator<T>
48. array<NavDestination> NavGraph::class.java uri R.id.fragmentA R.id.fragmentB R.id.graph2 NavDestination NavDestination NavDestination
49. array<NavDestination> NavGraph::class.java uri R.id.fragmentA R.id.fragmentB R.id.graph2 NavDestination NavDestination NavDestination
50. array<NavDestination> NavGraph::class.java uri R.id.fragmentA R.id.fragmentB R.id.graph2 NavDestination NavDestination NavDestination
51. array<NavDestination> NavGraph::class.java uri R.id.fragmentA R.id.fragmentB R.id.graph2 NavDestination NavDestination NavDestination NavDestination NavDestination <deeplink uri = uri> <Fragment>
52. array<NavDestination> <NavGraph id = R.id.graph> NavDestination Navigator<NavGraph> NavDestination NavDestination <deeplink uri = “uri”> <Fragment> R.id.fragmentA R.id.fragmentB NavDestination NavDestination NavDestination Navigator <Fragment>
53. array<NavDestination> <NavGraph id = R.id.graph> NavDestination Navigator<NavGraph> NavDestination NavDestination <deeplink uri = “uri”> <Fragment> R.id.fragmentA R.id.fragmentB NavDestination NavDestination NavDestination Navigator <Fragment> adds this fragment to backstack
54. Breaking rule #2: making graphs mutable
55. what if you don’t know where to go till runtime? Fragment A Fragment A ?? Fragment B Module
56. Fragment A Fragment B Fragment C Fragment E ??
57. you can modify graphs at runtime
63. Fragment A Fragment B Fragment C Fragment E NavDestination Fragment D Module
65. Breaking rule #3: Data sharing in non-traditional ways
66. How do fragments in the stack react to this unknown destination? Fragment A Fragment A ?? Fragment B What if Fragment B needs to know what happens in Fragment ?? They don’t share a ViewModel or Activity or data store
67. Fragment A Fragment A ?? Fragment B How do we share data across a backstack?
68. NavGraphViewModels
69. SavedStateHandle
70. NavBackStackEntry NavController SavedStateRegistry ViewModelStore NavDestination Fragment Backstack NavBackStackEntry NavBackStackEntry
72. Fragment A Fragment B
73. Fragment A Fragment B ??
74. Fragment A Fragment B
75. The fundamentals of Android navigation are the same: backstack, intents, etc What has changed: access and responsibilities Compose doesn’t change a whole lot regarding navigation